A friendly Monstro jumps on a random enemy, dealing 120 damage while destroying nearby obstacles like rocks.
Notes
This item will target Isaac if it is used in a room without monsters and can cause damage (a full-heart).
Monstro can be dodged in multiple ways depending on Speed and timing.
At 1.95 Speed or higher, Monstro can be dodged by walking in a straight line.
At 1.84 Speed or higher, Monstro can be dodged by standing still for a moment, and then moving.
At 1.69 Speed or higher, Monstro can be dodged by walking in one direction then walking in the opposite direction with the right timing.
At 0.86 Speed or higher, Monstro can be dodged by walking in a straight line.
At 0.62 Speed or higher, Monstro can be dodged by standing still for a moment, and then moving.
At 0.38 Speed or higher, Monstro can be dodged by walking in one direction then walking in the opposite direction with the right timing.
Monstro will target Shopkeepers. In Repentance you can also bait him into opening secret rooms or destroying tinted rock without hurting Isaac, if timed correctly. Pre-Repentance Monstro will home in on Isaac and hit him no matter what.
If Monstro falls near the entrance to a Secret Room, it will be opened. This can be used to open Secret Rooms without using Bombs.
Like Mom and Satan's stomp attacks, this attack is treated as an explosion, so Pyromaniac and Host Hat will be activated if Monstro falls on Isaac.
Judging by the sprites of Monstro/Monstro II, it can be assumed that the missing tooth is an incisor tooth or canine tooth. The item physically resembles a molar tooth however.
This item's unlock is the most common steam achievement in the game.
Monstro jumps on a random enemy, dealing 120 damage while destroying nearby obstacles like rocks.
At 1.95 Speed or higher, Monstro can be dodged by walking in a straight line.
At 0.86 Speed or higher, Monstro can be dodged by walking in a straight line.
Shopkeepers. In Repentance you can also bait him into opening secret rooms or destroying tinted rock without hurting Isaac, if timed correctly. Pre-Repentance Monstro will home in on Isaac and hit him no matter what.
Secret Room, it will be opened. This can be used to open 
Bombs.
Mom and 
Satan's stomp attacks, this attack is treated as an explosion, so 
Pyromaniac and 
Host Hat will be activated if Monstro falls on Isaac.
This item does not affect the boss, 
Book of Virtues: Spawns wisps in the middle ring, looking like teeth. These wisps shoot 50% slower than the average wisp, but deal 12 damage per shot.
Car Battery: Monstro deals double damage.
Monstro II's mouth.
II - The High Priestess, but deals less damage.
The Binding of Isaac: Rebirth
